The present invention relates generally to indicating devices, and more particularly to luminescent solid state status indicators capable of indicating a changing condition such as represented by a change in the magnitude of a signal voltage.
There are many consumer applications including automobiles, household appliances and the like wherein a meter has been replaced with a simple lamp circuit for purposes of economy. A familiar application of such a lamp circuit is as a substitute for the ammeter and oil pressure gauges in the typical automobile instrument panel. While the lamp is capable of indicating a faulty condition, such as battery discharge or dangerously low oil pressure, it cannot indicate a changing condition or, for that matter, the direction from which the change is taking place. Thus, economy has been realized at the sacrifice of the ability to transmit information to the operator of the automobile, appliance or the like.
It is highly desirable to provide a luminescent status indicator which is capable not only of indicating a faulty condition but is also capable of indicating a changing condition, e.g., where represented by a change in the magnitude of a signal voltage. Such a status indicator would not only be valuable in consumer applications but could be used for many measurements in industrial applications where a meter or gauge is presently being employed. In addition, where the preciseness of the measurement provided by a meter or gauge is required, such status indicators could be used in conjunction with the meter or gauge to attract the attention of the operator.
A luminescent solid state status indicator of the foregoing type is disclosed in the co-assigned application of the present inventors, Ser. No. 401,775, filed Sept. 28, 1973, and the luminescent solid state status indicator presently disclosed is an improvement of the indicator disclosed as claimed in the above-described application Ser. No. 401,775, now U.S. Pat. No. 3,873,979 (Craford et al.).